Downlink ppdu sending method and apparatus, and downlink ppdu receiving method and apparatus

ABSTRACT

A radio physical layer protocol data unit (PPDU) sending method includes: obtaining, a radio physical layer protocol data unit (PPDU), wherein the PPDU includes a high efficiency-signal field A (HE-SIG-A) and a high efficiency-signal field B (HE-SIG-B), the HE-SIG-A includes a field indicating a quantity of orthogonal frequency division multiplexing (OFDM) symbols in the HE-SIG-B, and wherein a value of the field indicates one of the following: that the quantity of OFDM symbols included in the HE-SIG-B is greater than or equal to 16, or the quantity of OFDM symbols included in the HE-SIG-B; and sending the PPDU.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2018/112869, filed on Oct. 31, 2018, which claims priority toChinese Patent Application No. 201711071408.8, filed on Nov. 3, 2017.The disclosures of the aforementioned applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

The present invention relates to the field of communicationstechnologies, and more specifically, to a downlink PPDU sending methodand apparatus, and a downlink PPDU receiving method and apparatus.

BACKGROUND

To significantly increase a service transmission rate in a WLAN system,in the institute of electrical and electronics engineers (IEEE) 802.11axstandard, an orthogonal frequency division multiple access (OFDMA)technology is further used based on an existing orthogonal frequencydivision multiplexing (OFDM) technology. A time-frequency resource of awireless channel on an air interface is divided into a plurality oforthogonal time-frequency resource unit (RU) in the OFDMA technology.The RUs may be shared in time domain and be orthogonal in frequencydomain.

The OFDMA technology supports a plurality of nodes in simultaneouslysending and receiving data. When an access point needs to transmit datawith a station, resources are allocated based on an RU or RU group.Different channel resources are allocated to different STAs at a samemoment, so that a plurality of STAs efficiently access channels, therebyincreasing channel utilization.

In an existing Wi-Fi system including an IEEE 802.11a-based legacysystem and an IEEE 802.11n-based HT system, uplink data transmission isonly point-to-point transmission, as shown in FIG. 1. To be specific, ata same moment, on a same channel, or in a same spectrum segment, onlyone STA transmits data to the AP. Downlink data transmission is alsopoint-to-point transmission. To be specific, at a same moment or in asame spectrum segment, the AP transmits data to only one STA. However,in a next-generation Wi-Fi system, or in a HEW system, after the OFDMAtechnology is introduced, uplink data transmission is no longerpoint-to-point transmission, but multipoint-to-point transmission, asshown in FIG. 2. To be specific, at a same moment, on a same channel, orin a same spectrum segment, a plurality of STAs simultaneously transmitdata to the AP. Downlink data transmission is also no longer apoint-to-point transmission, but point-to-multipoint transmission.

For an OFDMA-based WLAN system, a time-frequency resource needs to beefficiently indicated to the STA.

SUMMARY

Embodiments of the present invention provide a downlink PPDU sendingmethod and apparatus and a downlink PPDU receiving method and apparatus,to support reduction of transmission resource overheads caused byresource scheduling.

An embodiment of the present invention provides a plurality of solutionsused to resolve the foregoing technical problem. A radio physical layerprotocol data unit PPDU sending method includes: obtaining, by a sendingapparatus, a radio physical layer protocol data unit PPDU, where thePPDU includes a high efficiency-signal field A and a highefficiency-signal field B HE-SIG-B, the HE-SIG-A includes a field usedto indicate a quantity of OFDM symbols in the HE-SIG-B, and whendifferent MCSs are used, or whether DCM is used, or different bandwidthsare used for HE-SIG-B field transmission, a same value in the field usedto indicate the quantity of OFDM symbols in the HE-SIG-B indicatesdifferent quantities of OFDM symbols; and sending the PPDU, so that areceiving apparatus determines, with reference to the different MCSs, orwhether the DCM is used, or the different bandwidths and based on avalue of the field used to indicate the quantity of OFDM symbols in theHE-SIG-B, the quantity of OFDM symbols in the HE-SIG-B.

Correspondingly, an embodiment of the present invention further providesan apparatus that may be configured to perform the foregoing method, anda method and an apparatus on a receiver side. Details are not describedherein again. An embodiment of the present invention also provides acorresponding computer readable storage medium, configured to implementone of methods mentioned in all implementations.

According to the PPDU sending method and apparatus in the embodiments ofthe present invention, OFDMA transmission in a WLAN system can beproperly and efficiently completed.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the presentinvention more clearly, the following briefly describes the accompanyingdrawings required for describing the embodiments or the prior art.Apparently, the accompanying drawings in the following description showmerely some embodiments of the present invention, and a person ofordinary skill in the art may derive other drawings from theseaccompanying drawings without creative efforts.

FIG. 1 is a simple schematic diagram of point-to-point transmission in aWLAN system;

FIG. 2 shows multipoint-to-point transmission in another WLAN system(for example, a HEW);

FIG. 3 is a simple schematic structural diagram of a downlinkmulti-station PPDU frame according to an embodiment of the presentinvention (compliant with 802.11ax);

FIG. 4 is a schematic structural diagram of an HE-SIG-B content channel;

FIG. 5 is a simple schematic structural diagram of a sending apparatus;and

FIG. 6 is a simple schematic structural diagram of a receivingapparatus.

DESCRIPTION OF EMBODIMENTS

The following clearly describes technical solutions in embodiments ofthe present invention with reference to accompanying drawings in theembodiments of the present invention. Apparently, the describedembodiments are some but not all of the embodiments of the presentinvention. All other embodiments obtained by a person of ordinary skillin the art based on the embodiments of the present invention withoutcreative efforts shall fall within the protection scope of the presentinvention.

Acronyms and Abbreviations

Acronyms and abbreviations Complete English Chinese Englishexpression/English expression/Chinese abbreviation standard term term APAccess point Access point STA Station Station OFDM Orthogonal frequencyOrthogonal frequency division multiplexing division multiplexing OFDMAOrthogonal frequency Orthogonal frequency division multiple divisionmultiple access access FD Full duplex Full duplex WLAN Wireless localaccess Wireless local access network network RU Resource unit Resourceunit DL Downlink Downlink UL Uplink Uplink TXOP Transmit opportunityTransmission opportunity NG Next generation Next generation MAC Mediumaccess control Medium access control MU Multiple user Multiple user PPDUPHY protocol data unit PHY protocol data unit VHT Very high throughputVery high throughput L-STF Legacy-short training field Legacy-shorttraining field L-LTF Legacy-long training field Legacy-long trainingfield L-SIG Legacy-signal field Legacy-signal field RL-SIG Repeatedlegacy-signal Repeated legacy-signal field field HE-SIG-A Highefficient-signal High efficiency-signal field A field A HE-SIG-B Highefficient-signal High efficiency-signal field B field B HE-STF Highefficient-short High efficiency-short training field training fieldHE-LTF High efficient-long High efficiency-long training field trainingfield

A sending apparatus in each implementation, for example, may be anaccess point (AP) in a WLAN, and the AP may also be referred to as awireless access point, a bridge, a hotspot, or the like, and may accessa server or a communication network.

As a receiving apparatus, for example, the receiving apparatus may be auser station (STA) in the WLAN, and the STA may also be referred to as auser, and may be a wireless sensor, a wireless communications terminal,or a mobile terminal, for example, a mobile phone (or referred to as a“cellular” phone) and a computer having a wireless communicationfunction. For example, the receiving apparatus may be a portable,pocket-sized, handheld, computer built-in, wearable, or vehicle-mountedwireless communications apparatus that exchanges communication data suchas voice and/or data with a radio access network.

It should be understood that the foregoing enumerated system applicableto a method in the embodiments of the present invention is merely anexample for description, and the present invention is not limitedthereto. For example, the following may be further enumerated; a globalsystem for mobile communications (GSM), a code division multiple access(CDMA) system a wideband code division multiple access (WCDMA) system, ageneral packet radio service (GPRSsystem, a long term evolution (LTE)system.

Correspondingly, a network device may be an access point, and this isnot limited in the present invention. A terminal device may be a mobileterminal, or mobile user equipment, for example, a mobile phone (orreferred to as a “cellular” phone).

A downlink PPDU sent by the AP in each implementation of the presentinvention complies with the 802.11ax standard, and this can ensurecompatibility with a transmission frame format in a conventional Wi-Fisystem. As shown in FIG. 3, a frame format of the PPDU includes alegacy-preamble part Legacy-preamble, a high efficiency-signal field A(HE-SIG-A), a high efficiency-signal field B (HE-SIG-B), a highefficiency-short training field (HE-STF), a high efficiency-longtraining field (HE-LTF), and a data field. The legacy-preamble includesa legacy-short training field (L-STF), a legacy-long training field(L-LTF), and a legacy-signal field (L-SIG).

It should be noted that, based on an indication of a subfield includedin the HE-SIG-A, a quantity of OFDM symbols included in the HE-SIG-Bfield is changeable, and fields preceding the HE-SIG-B field eachinclude a fixed quantity of OFDM symbols. For example, the HE-SIG-Aincludes two quantities of OFDM symbols. The aforementioned subfield inthe HE-SIG-A is used to indicate the quantity of OFDM symbols includedin the HE-SIG-B field. A length of the subfield is fixed, and thesubfield occupies four bits, for example, B18-B21.

In an embodiment of the present invention, transmission bandwidthsinclude 20 M, 40 M, 80 M, 160 M. and four puncturing modes in the 80 Mand 160 M bandwidths. Resource units that may be obtained throughdivision of the 20 M bandwidth include a 26 resource unit, a 52 resourceunit, a 106 resource unit, and a 242 resource unit, the foregoingseveral different resource units may be combined into the 20 Mbandwidth, and the 20 M bandwidth may be divided into a maximum of nine26 resource units (which includes 26 subcarriers, and is a smallest ofall types of resource units). Resource units that may be obtainedthrough division of the 40 M bandwidth include a 26 resource unit, a 52resource unit, a 106 resource unit, a 242 resource unit, and a 484resource unit, the foregoing several different resource units may becombined into the 40 M bandwidth, and the 40 M bandwidth may be dividedinto a maximum of eighteen 26 resource units. Resource units that may beobtained through division of the 80 M bandwidth include a 26 resourceunit, a 52 resource unit, a 106 resource unit, a 242 resource unit, a484 resource unit, and a 996 resource unit, and the foregoing severaldifferent resource units may be combined into the 80 M bandwidth, andthe 80 M bandwidth may be divided into a maximum of thirty-seven 26resource units. Resource units that may be obtained through division ofthe 160 M bandwidth include a 26 resource unit, a 52 resource unit, a106 resource unit, a 242 resource unit, a 484 resource unit, a 996resource unit, and a 996*2 resource unit, and the foregoing severaldifferent resource units may be combined into the 160 M bandwidth, andthe 160 M bandwidth may be divided into a maximum of seventy-four 26resource units. Specifically, reference may be made to the 802.11axstandard, and details are not described herein again.

In a transmission process, if a bandwidth is greater than thefundamental channel of 20 MHz, the legacy-preamble, an RL-SIG, and theHE-SIG-A are replicated and transmitted on each 20 MHz channel. However,the HE-SIG-B is transmitted on each 20 MHz channel in a [1 2 1 2]manner. Specifically, when the bandwidth is 20 M, the HE-SIG-B includesonly one HE-SIG-B content channel, and the HE-SIG-B content channel istransmitted on the 20 M channel. When the bandwidth is greater than 20M, the HE-SIG-B includes only two HE-SIG-B content channels, and eachHE-SIG-B content channel includes a same quantity of OFDM symbols. OneHE-SIG-B content channel is transmitted on an odd-numbered 20 M channel(HE-SIG-B 1 for short), and includes resource allocation information(located in a common field common field) of a plurality of odd-numbered20 M channels and user fields (located in a user specific field userspecific field) transmitted on the plurality of odd-numbered 20 Mchannels. The other HE-SIG-B content channel is transmitted on aneven-numbered 20 M channel (HE-SIG-B2 for short), and includes resourceallocation information of a plurality of even-numbered 20 M channels anduser fields transmitted on the plurality of even-numbered 20 M channels.In addition, quantities of bits included in the two HE-SIG-B contentchannels need to be same, and if the quantity of bits included in oneHE-SIG-B content channel is longer than the quantity of bits included inthe other HE-SIG-B content channel, a short HE-SIG-B content channelneeds to be padded with a bit for alignment.

Referring to FIG. 4, an HE-SIG-B content channel includes a common fieldand a user specific field. The common field includes 8*N-bit resourceallocation information of an odd-numbered or even-numbered 20 M channel(N is a quantity of the odd-numbered or even-numbered 20 M channels), a1-bit indication indicating whether a 26 resource unit in 80 MHz or in80 M of a 160 M bandwidth is used, a 4-bit cyclic redundancy check codefield, and a 6-bit tail bit field. The user specific field furtherincludes a user block field. In addition to the last user block field,each user block field further includes two user fields, a cyclicredundancy check code field, and a tail bit field. The last user blockfield may include one or two user fields, a 4-bit cyclic redundancycheck code field, and a 6-bit tail bit field. The user field includes 21bits. Therefore, the user specific field includes Z*21+ceil(Z/2)*10bits, where Z is a quantity of stations included in the HE-SIG-B contentchannel (including a dummy station, where the dummy station is a stationcorresponding to another unused resource unit other than an unusedresource unit indicated in the common field), and ceil( ) is roundingup.

Therefore, a quantity of bits included in the entire HE-SIG-B contentchannel is:

8*N+a+10+Z*21+ceil(Z/2)*10  Formula 1

where when the bandwidth is 80 M or 160 M, a=1; otherwise, a=0.

The common field includes resource allocation information, and is usedto indicate the RU assignment. The user field included in a userspecific field is in a one-to-one correspondence with the severalresource units obtained through division. For example, the bandwidthspectrum resource is divided into two resource units, and a user fieldincluded in the user specific field is a station 1 information field anda station 2 information field, and it means that data of a station 1 istransmitted on the first resource unit, and data of a station 2 istransmitted on the second resource unit.

If a plurality of stations are invoked in downlink OFDMA, it means thata quantity of information bits included in each HE-SIG-B content channelis excessive, and consequently, the quantity of OFDM symbols included inthe HE-SIG-B field is excessive. Therefore, a large quantity of bitsneed to be spent in the HE-SIG-A field to indicate the quantity of OFDMsymbols of the following HE-SIG-B field. However, a quantity of bitsincluded in the HE-SIG-A is limited.

Specifically, an HE-SIG-A stipulated in the 802.11ax draft 2.0 versionis used an example, and an HE-SIG-A field in a downlink multi-stationPPDU frame in 802.11ax is as follows:

HE-SIG-A Quantity symbol Bit Field of bits HE-SIG-A 1 B0 Uplink/Downlink1 B1-B3 HE-SIG-B modulation coding 3 B4 HE-SIG-B dual-carrier 1modulation B5-B10 BSS (basic service set) color 6 B11-B14 Space divisionmultiplexing 4 B15-B17 Bandwidth 3 B18-B21 HE-SIG-B symbol quantity or 4multi-user multiple-input multiple-output station quantity B22 HE-SIG-Bcompression 1 B23-B24 Sideband interval + long 2 training field size B25Doppler 1 HE-SIG-A 2 B0-B6 Transmission opportunity 7 B7 Reservation 1B8-B10 HE-LTF quantity and 3 midamble period B11 Low-densityparity-check 1 code extra symbol B12 Space division time coding 1B13-B14 Padding factor before forward 2 error correction coding B15Fuzziness of padding and 1 expansion B16-B19 Cyclic redundancy checkcode 4 B20-B25 Tail bit 6

In the HE-SIG-A 1 in the existing 802.11ax draft 2.0 version, when avalue of a B22 is 0, a value of the B18-B21 is a quantity of symbols inthe HE-SIG-B minus 1; and when the value of B22 is 1, the value of theB18-B21 is a quantity of stations participating in multi-usermultiple-input multiple-output transmission minus 1. To be specific,four bits are used by the HE-SIG-A to indicate the quantity of symbolsin the HE-SIG-B, and a maximum of 16 OFDM symbols can be indicated.

However, the foregoing technical solution has the following problems:

Through calculation, when an MCS0 and dual-carrier modulation are usedfor the HE-SIG-B, 16 OFDM symbols can carry 208-bit data, when the MCS0,or an MCS1 and the dual-carrier modulation are used for the HE-SIG-B, 16OFDM symbols include 416-bit data, and when the MCS1, or an MCS2 and thedual-carrier modulation are used for the HE-SIG-B, 16 OFDM symbolsinclude 832-bit data. The foregoing bit data does not include a pilotbit.

When the bandwidth is 160 M, four odd-numbered 20 M channels and foureven-numbered 20 M channels are included. Based on Formula 1, if theMCS0 and the dual-carrier modulation are used for the HE-SIG-B,

8*N+a+10+ceil(X)*21+ceil(ceil(X)*/2)*10<=208  Formula 2

Herein, N=4, a=1, and X is a total quantity of user fields included inthe HE-SIG-Bin the PPDU of the 160 M bandwidth. It should be noted thatX is based on that user field two HE-SIG-B content channels each includea same quantity of user fields. If the quantities of user fieldsincluded in the two HE-SIG-B content channels are different, a shortHE-SIG-B content channel needs to be padded with a garbage bit to alignwith a long HE-SIG-B content channel in length. Therefore, an actualquantity of user fields included in the HE-SIG-B is less than X. X<=12is obtained through calculation. Therefore, if the MCS0 and thedual-carrier modulation are used for the HE-SIG-B, a maximum quantity ofstations that can be scheduled in the 160 M bandwidth cannot exceed 12.

However, 160 M, 80 M, and 40 M bandwidths can be divided into a maximumof 74, 32, and 18 resource units, and a type of each resource unit is aminimum 26 resource unit. In other words, 74, 32, and 18 stations areallowed to be scheduled. However, a maximum quantity of stationsscheduled in downlink OFDMA is 12 due to an upper limit of a quantity ofsymbols in the existing HE-SIG-B, thereby reducing a multi-userdiversity gain caused by an OFDMA technology. It should be noted that,because the 20 M bandwidth can be divided into a maximum of 9 resourceunits, and therefore, the 20 M bandwidth is not limited by the upperlimit of the quantity of symbols in the existing HE-SIG-B.

Embodiment 1

As mentioned in the foregoing technical solution, the HE-SIG-B symbolquantity field B18-B21 in the existing HE-SIG-A 1 field can indicate amaximum of 16 OFDM symbols included in the HE-SIG-B. As a result, amaximum of 12 stations can be scheduled in the 80 M or 160 M bandwidth.If excessive stations are scheduled in the downlink OFDMA, andconsequently, the quantity of symbols in the HE-SIG-B is greater than16. However, in this case, a receiver still performs execution accordingto an indication of the HE-SIG-B symbol quantity field in the HE-SIG-A 1field. As a result, the receiver misdetermines an end bit (end position)of the HE-SIG-B, and incorrectly receives a data packet.

To avoid the foregoing problem, an implementation of the presentinvention is provided, and includes the following steps.

On a transmitter side:

101. A sending apparatus obtains a radio physical layer protocol dataunit PPDU, where the PPDU includes a high efficiency-signal field AHE-SIG-A and a high efficiency-signal field B HE-SIG-B; and the HE-SIG-Aincludes a field (for example, a field B18-B21) used to indicate aquantity of OFDM symbols in the HE-SIG-B.

For a field (for example, the field B18-B21) used to indicate a quantityof OFDM symbols in the HE-SIG-B in the HE-SIG-A field, when a value ofthe field is a specific value (for example, when the B18-B21 in theHE-SIG-A is 15, in other words, “1111”), the value is used to indicatethat the quantity of OFDM symbols included in the HE-SIG-B is greaterthan or equal to 16; and when a value of the field is another value, thevalue is used to indicate the quantity of OFDM symbols included in theHE-SIG-B. For example, when the B18-B21 in the HE-SIG-A is any one of 0to 14, the quantity of OFDM symbols included in the HE-SIG-B is equal tothe value of the field B18−B21+1.

102. Send the PPDU, so that a receiving apparatus determines, based onat least the field that is included in the HE-SIG-A and that is used toindicate the quantity of OFDM symbols in the HE-SIG-B, an end positionof the HE-SIG-B.

On a receiver side, the method includes the following steps.

103. Receive a radio physical layer protocol data unit PPDU, where thePPDU includes a high efficiency-signal field A HE-SIG-A and a highefficiency-signal field B HE-SIG-B, and the HE-SIG-A includes a field(for example, a field B18-B21) used to indicate a quantity of OFDMsymbols in the HE-SIG-B.

Specifically, the HE-SIG-A may further include one or a combination ofthe following information: an MCS used for the HE-SIG-B, whether DCM isused for the HE-SIG-B, or a current bandwidth for the HE-SIG-B.

104. A receiving apparatus determines, based on the received HE-SIG-A,the quantity of OFDM symbols in the HE-SIG-B (or an end position of theHE-SIG-B field).

Specifically, based on the received HE-SIG-A field, if a value of anHE-SIG-B symbol quantity field (namely, the B18-B21) is 0 to 14, aquantity M of OFDM symbols of the following HE-SIG-B field is directlydetermined. Specifically, M is the value of the HE-SIG-B symbol quantityfield (namely, the B18-B21) in the HE-SIG-A field+1. If the value of theHE-SIG-B symbol quantity field (namely, the B18-B21) is 15, stationquantity information is obtained by reading a common field in theHE-SIG-B, to infer, based on the station quantity information, thequantity of OFDM symbols included in the HE-SIG-B.

In an example, the foregoing inference method includes: The HE-SIG-Bfield includes two HE-SIG-B content channels, namely, the HE-SIG-B 1 andthe HE-SIG-B2 described above. In this case, the quantity of OFDMsymbols in the HE-SIG-B field depends on an HE-SIG-B content channelthat includes a larger quantity of user fields. Therefore, the receivingapparatus needs to read common fields separately included in each of thetwo HE-SIG-B content channels, and accumulate, based on 8-bit resourceallocation information of every 20 M channel included in the two commonfields, a quantity of stations on each divided resource unit, therebyobtaining the user field included in each HE-SIG-B content channel(including another unused resource unit other than an unused resourceunit indicated by the common field, and in this case, the quantity ofuser fields is 1).

Based on the HE-SIG-B content channel that includes the maximum of userfields (the other HE-SIG-B content channel is padded to align with theHE-SIG-B content channel in length), a quantity of bits of the HE-SIG-Bcontent channel is obtained based on Formula 1, and then a quantity ofbits included in each OFDM symbol is obtained based on the MCS used bythe HE-SIG-B and whether the DCM is used, thereby obtaining a quantityof OFDM symbols included in the HE-SIG-B content channel. Finally, thequantity of symbols included in the HE-SIG-B field is obtained.

For ease of understanding, an example is used to describe the foregoingsolution. A downlink OFDMA PPDU of a channel of an 80 M bandwidth isused an example, the 80 M channel sequentially includes a first channel,a second channel, a third channel, and a fourth channel that each are of20 M bandwidth. In a table of resource allocation information of thecommon field in the HE-SIG-B based on the 802.11ax draft 2.0, the commonfield in each HE-SIG-B content channel includes: two resource allocationsequences, where the resource allocation sequence is specific for each20 M channel, and a length of each resource allocation sequence is eightbits; a 1-bit indication indicating whether a 26 resource unit in 80 Mis used; a 4-bit cyclic redundancy check code; and a 6-bit tail bit.Because the resource allocation sequence and the indication indicatingwhether the 26 resource unit in the 80 M is used are related to aquantity of station information included in each HE-SIG-B contentchannel, it is assumed that only the two factors are considered below.Assuming that the MCS0 and the DCM are used for HE-SIG-B transmission,and

when resource allocation sequences of the HE-SIG-B content channel 1(HE-SIG-B 1 for short) are “00000000”, “11001001”, and “0”, meaningindicated by the three sequences is as follows: the first sequenceindicates that the first 20 M channel is divided into nine 26 resourceunits, and each 26 resource unit is transmitted by only one station; thesecond sequence indicates that the third 20 M channel and the fourth 20M channel are combined into a 484 resource unit, and in stationstransmitting the 484 resource unit, information fields of two stationsare included in the HE-SIG-B 1; and the third sequence indicates thatthe 26 resource unit in the 80 M bandwidth is not used, but there is nocorresponding dummy user field; and

when resource allocation sequences of the HE-SIG-B content channel 2(HE-SIG-B2 for short) are “00000001”, “11001101”, and “0”, meaningindicated by the three sequences is as follows: the first sequenceindicates that the second 20 M channel is divided into seven 26 resourceunits and one 52 resource unit, and each of the 26 resource unit and 52resource unit is transmitted by only one station; the second sequence iscorresponding to the fourth 20 M channel, and indicates that the third20 M channel and the fourth 20 M channel are combined into a 484resource unit, and in stations transmitting the 484 resource unit,information fields of six stations are included in the HE-SIG-B2; andthe third sequence indicates that the 26 resource unit in the 80 Mbandwidth is not used, but there is no corresponding dummy user field.

The meaning indicated by the foregoing sequence indications is based onthe 802.11ax draft 2.0.

The foregoing two HE-SIG-B content channels are received and correctlydecoded, to learn that the quantity of user fields included in theHE-SIG-B content channel 1 is 11, and the quantity of user fieldsincluded in the HE-SIG-B content channel 2 is 14. Therefore, a stationcalculates a quantity of OFDM symbols in the HE-SIG-B by using 14 (alarger one of the two) user fields, and based on Formula 1, a quantityof information bits included in the HE-SIG-B is 391 bits, where N=2,Z=14, and a=1. Each OFDM symbol in the HE-SIG-B for which the MCS0 andthe DCM are used includes 13 bits, so that the receiver may learn that31 OFDM symbols are required for the HE-SIG-B.

Embodiment 2

In another alternative implementation, a problem that a field in theHE-SIG-A cannot indicate a quantity of all OFDM symbols in the HE-SIG-Bmay also be resolved.

In this implementation, fields and functions of the HE-SIG-A and theHE-SIG-B are the same as those described above. To avoid a conflict thatthe quantity of symbols in the HE-SIG-B exceeds the maximum quantity 16indicated by the HE-SIG-B symbol quantity field B18-B21 in the HE-SIG-A1 field due to excessive stations scheduled in the downlink OFDMA, themaximum quantity of stations scheduled in the downlink OFDMA may belimited.

For example, for the 160 M or 80 M bandwidth, a lowest rate, and theMCS0 and the DCM are used for the HE-SIG-B transmission. To be specific,the HE-SIG-B is allowed to include 16*13=208 bits. Based on Formula 1,in the 160 M or 80 M bandwidth, a maximum quantity of stations that areallowed to be invoked is X.

8*N+a+10+ceil(X/2)*21+ceil(ceil(X/2)/2)*10<=208  Formula 3

where N=4 or N=2, a=1, and X=12 is obtained through calculation.

For another example, for the 40 M bandwidth, a lowest rate, and the MCS0and the DCM are used for the HE-SIG-B transmission. To be specific, theHE-SIG-B is allowed to include 16*13=208 bits. Based on Formula 1, inthe 40 M bandwidth, a maximum quantity of stations that are allowed tobe invoked is X.

8*N+a+10+ceil(X/2)*21+ceil(ceil(X/2)/2)*10<=208  Formula 3

where N=1 and a=0, and X=14 is obtained through calculation.

It should be noted that X is based on that two HE-SIG-B content channelseach include a same quantity of user fields. If the quantities of userfields included in the two HE-SIG-B content channels are different, ashort HE-SIG-B content channel needs to be padded with a garbage bit toalign with a long HE-SIG-B content channel in length. Therefore, anactual quantity of user fields included in the HE-SIG-B is less than X.

Considering that the DCM is optional in the 802.11ax, when the DCM isnot supported, the lowest transmission rate of the HE-SIG-B is the MCS0.To be specific, the HE-SIG-B is allowed to include 16*26=416 bits. Basedon the foregoing same calculation, in the 160 M or 80 M bandwidth, amaximum quantity of stations that are allowed to be invoked is 28. Amaximum quantity of stations that are allowed to be scheduled in the 40M bandwidth or a 20 M bandwidth is greater than a quantity of resourceunits that may be obtained by dividing the bandwidth. Therefore, themaximum quantity of stations that are allowed to be scheduled does notneed to be limited.

In conclusion, the following solution may be used to avoid a problemthat the quantity of OFDM symbols in the HE-SIG-B exceeds the maximumquantity (to be specific, 16) indicated by the HE-SIG-B symbol quantityfield (namely, the B18-B21) in the HE-SIG-A 1 field due to excessivestations scheduled in the downlink OFDMA.

When the DCM is used for the HE-SIG-B, for the 160 M or 80 M bandwidth,the maximum quantity of stations that are allowed to be invoked is 12,and for the 40 M bandwidth, the maximum quantity of stations that areallowed to be invoked is 14. Alternatively, for the 160 M, 80 M, or 40 Mbandwidth, the maximum quantity of stations that are allowed to bescheduled is 12, and there is no limitation for another bandwidth.

2. When the DCM is not used for the HE-SIG-B, for the 160 M or 80 Mbandwidth, the maximum quantity of stations that are allowed to beinvoked is 28, and there is no limitation for another bandwidth.

It should be noted that the foregoing quantity of stations iscorresponding to a quantity of user fields of the HE-SIG-B. In otherwords, the foregoing quantity of stations includes a quantity of dummystations and a quantity of stations that actually participate inscheduling transmission.

Certainly, in an alternative solution, regardless of whether the DCM isused for the HE-SIG-B transmission, the solution may be directlyperformed according to the limitation 1. In other words, regardless ofwhether the DCM is used for transmission, for the 160 M or 80 Mbandwidth, the maximum quantity of stations that are allowed to beinvoked is 12, and for the 40 M bandwidth, the maximum quantity ofstations that are allowed to be invoked is 14. Alternatively, for the160 M, 80 M. or 40 M bandwidth, the maximum quantity of stations thatare allowed to be scheduled is 12.

Embodiment 3

To resolve the foregoing technical problem, an embodiment of the presentinvention provides a method for efficiently indicating the end location(equivalent to obtaining the quantity of OFDM symbols) of the HE-SIG-B.On a transmitter side: a radio physical layer protocol data unit PPDUsending method includes the following steps.

301. A sending apparatus generates a radio physical layer protocol dataunit PPDU, where the PPDU includes a high efficiency-signal field BHE-SIG-B, the HE-SIG-B includes a common field and a user specificfield, and the user specific field includes one or more user fields. Inaddition, after the last user field, the HE-SIG-B includes informationused to indicate that the HE-SIG-B ends.

302. Send the PPDU, so that a receiving apparatus determines an endposition of the HE-SIG-B based on the information used to indicate thatthe HE-SIG-B ends.

In a specific example, the PPDU includes a high efficiency-signal fieldA, and the HE-SIG-A includes a field used to indicate a quantity of OFDMsymbols of the HE-SIG-B. A specific value of the field used to indicatethe quantity of the OFDM symbols of the HE-SIG-B is used to indicate:the HE-SIG-B includes the information used to indicate that the HE-SIG-Bends, and another value (any value other than the specific value) of thefield used to indicate the quantity of OFDM symbols of the HE-SIG-B isused to indicate: the HE-SIG-B does not include the information used toindicate that the HE-SIG-B ends.

More specifically, a length of the information used to indicate that theHE-SIG-B ends is the same as a length of the user field. In an example,the information used to indicate that the HE-SIG-B ends starts with an11-bit special station identifier AID, for example, 2044 or 2043. Thequantity of symbols in the HE-SIG-B may be indicated by using another 10bits, or several bits such as seven or eight bits, or all bits. In thiscase, when performing reception, a station needs to correctly decodeonly an HE-SIG-B content channel on which the station is located, andthen knows the quantity of symbols in the HE-SIG-B. On a receiver side,correspondingly, a radio physical layer protocol data unit PPDUreceiving method includes the following steps.

303. A receiving apparatus receives a radio physical layer protocol dataunit PPDU, where the PPDU includes a high efficiency-signal field BHE-SIG-B, and the HE-SIG-B includes a common field common field and auser specific field user specific field, and the user specific fielduser specific field includes one or more user fields. In addition, afterthe last user field, the HE-SIG-B includes information used to indicatethat the HE-SIG-B ends.

304. The receiving apparatus determines, based on at least theinformation used to indicate that the HE-SIG-B ends, an end position ofthe HE-SIG-B.

Specifically, the PPDU includes a high efficiency-signal field A, andthe HE-SIG-A includes a field used to indicate a quantity of OFDMsymbols in the HE-SIG-B. and the field used to indicate the quantity ofOFDM symbols in the HE-SIG-B is a specific value or another value. Thereceiving apparatus reads, based on the specific value, the informationused to indicate that the HE-SIG-B ends to determine the end position ofthe HE-SIG-B. Alternatively, the receiving apparatus determines, basedon the quantity of OFDM symbols in the HE-SIG-B indicated by the anothervalue, the end position of the HE-SIG-B.

As described in the method on the transmitter side, a length of theinformation used to indicate that the HE-SIG-B ends is the same as alength of the user field. In a specific example, the information used toindicate that the HE-SIG-B ends starts with an 11-bit-long specialstation identifier AID.

Embodiment 4

In another implementation, a radio physical layer protocol data unitPPDU sending method is provided, and the method includes the followingsteps.

401. A sending apparatus obtains a radio physical layer protocol dataunit PPDU, where the PPDU includes a high efficiency-signal field AHE-SIG-A and a high efficiency-signal field B HE-SIG-B; and the HE-SIG-Aincludes a field (for example, a field B18-B21) used to indicate aquantity of OFDM symbols in the HE-SIG-B.

When different MCSs are used, or whether DCM (dual carrier modulation,dual carrier modulation) is used, or different bandwidths are used forHE-SIG-B field transmission, a same value in the field used to indicatethe quantity of OFDM symbols in the HE-SIG-B indicates differentquantities of OFDM symbols.

402. Send the PPDU is sent, so that a receiving apparatus determines,with reference to the different MCSs, whether the DCM is used, or thedifferent bandwidth and based on the value of the field used to indicatethe quantity of OFDM symbols of the HE-SIG-B, the quantity of OFDMsymbols in the HE-SIG-B.

Specifically, the field used to indicate the quantity of OFDM symbols ofthe HE-SIG-B indicates different quantities of OFDM symbols according todifferent cases.

A quantity of symbols in the HE-SIG-B=ceil(the value of the field usedto indicate the quantity of OFDM symbols in the HE-SIG-B+1)*coefficientfactor, where the coefficient factor depends on the MCS used for theHE-SIG-B field transmission, whether the DCM is used for the HE-SIG-Bfield transmission, and the bandwidth used for the HE-SIG-B fieldtransmission. The HE-SIG-A includes an indication indicating that theMCS is used for the HE-SIG-B field transmission, whether the DCM isused, and the bandwidth is used (for example, separately indicated byB1-B3, a B4, and B15-B17 bits in an HE-SIG-A 1 field).

On a receiver side, the method includes the following steps.

403. Receive a radio physical layer protocol data unit PPDU, where thePPDU includes a high efficiency-signal field A HE-SIG-A and a highefficiency-signal field B HE-SIG-B, and the HE-SIG-A includes a field(for example, a field B18-B21) used to indicate a quantity of OFDMsymbols in the HE-SIG-B.

Specifically, the HE-SIG-A may further include one or a combination ofthe following information: an MCS used for the HE-SIG-B, whether DCM isused for the HE-SIG-B, or an operating bandwidth used for the HE-SIG-B.

404. A receiving apparatus determines, with reference to different MCSs,whether the DCM is used, or the operating bandwidth used for theHE-SIG-B and based on a value of the field used to indicate the quantityof OFDM symbols of the HE-SIG-B, the quantity of OFDM symbols in theHE-SIG-B.

Specific description is as follows: When an MCS0 and the DCM are usedfor HE-SIG-B field transmission, a quantity of data subcarriers(excluding pilot bits) included in each OFDM symbol is 13 bits.

When the MCS0 is used and no DCM is used for the HE-SIG-B fieldtransmission, or when an MCS1 and the DCM are used, a quantity of datasubcarriers (excluding pilot bits) included in each OFDM symbol is 26bits.

When the MCS1 is used and no DCM is used for the HE-SIG-B fieldtransmission, or when an MCS2 and the DCM are used, a quantity of datasubcarriers (excluding pilot bits) included in each OFDM symbol is 52bits.

Example 1: A Bandwidth is 160 M (Including Two Puncturing Modes in the160 M)

Based on Formula 1, for example, the current 160 M bandwidth is dividedinto a maximum of 74 resource units, and a quantity of information bitsincluded in an HE-SIG-B content channel is 1010 bits, where N=4, a=1,and Z=37 in Formula 1.

Therefore, according to the quantity of data subcarriers included ineach OFDM symbol in the foregoing cases in which the different MCSs areused and whether the DCM is used, the following may be obtained.

If the MCS0 and the DCM are used for the HE-SIG-B field transmission, 78OFDM symbols in the HE-SIG-B are required.

If the MCS0 (no DCM), or the MCS1 and the DCM are used for the HE-SIG-Bfield transmission, 39 OFDM symbols in the HE-SIG-B are required.

If the MCS1 (no DCM), or the MCS2 and the DCM are used for the HE-SIG-Bfield transmission, 20 OFDM symbols in the HE-SIG-B are required.

In other cases, a required quantity of OFDM symbols in the HE-SIG-B isless than 16, and the required quantity is not limited by a length ofthe field (for example, the field B18-B21) that is in the HE-SIG-A 1 andthat is used to indicate the quantity of OFDM symbols in the HE-SIG-B.

Based on the foregoing calculation, when the bandwidth is 160 M, and theMCS0 and the DCM are used for the HE-SIG-B field transmission, thecoefficient factor is 4.875. To be specific, the quantity of OFDMsymbols in the HE-SIG-B=ceil {(a value of the B18-B21+1)*4.875}.Specifically, a correspondence between the value of the B18-B21 in theHE-SIG-A 1 and the quantity of OFDM symbols in the HE-SIG-B indicated bythe value of the B18-B21 is shown in the following Table 1.

TABLE 1 Value obtained after multiplying the Value of the B18-B21coefficient factor (the quantity of in the HE-SIG-A 1 OFDM symbols inthe HE-SIG-B) 0 5 1 10 2 15 3 20 4 25 5 30 6 35 7 39 8 44 9 49 10 54 1159 12 64 13 69 14 74 15 78

When the bandwidth is 160 M, the MCS0 is used and no DCM is used for theHE-SIG-B field transmission, or when the bandwidth is 160 M, the MCS1and the DCM are used, the coefficient factor is 2.4375. To be specific,the quantity of symbols in the HE-SIG-B=ceil{(the value of theB18-B21+1)*2.4375}, and the foregoing correspondence is shown in thefollowing Table 2.

TABLE 2 Value obtained after multiplying the Value of the B18-B21coefficient factor (the quantity of in the HE-SIG-A 1 OFDM symbols inthe HE-SIG-B) 0 3 1 5 2 8 3 10 4 13 5 15 6 18 7 20 8 22 9 25 10 27 11 3012 32 13 35 14 37 15 39

When the bandwidth is 160 M, the MCS1 is used and no DCM is used for theHE-SIG-B field transmission, or when the bandwidth is 160 M, the MCS2and the DCM are used, the coefficient factor is 1.25. To be specific,the quantity of symbols in the HE-SIG-B=ceil{(the value of theB18-B21+1)*1.25}, and a specific correspondence is shown in thefollowing Table 3.

TABLE 3 Value obtained after multiplying the Value of the B18-B21coefficient factor (the quantity of in the HE-SIG-A 1 OFDM symbols inthe HE-SIG-B) 0 2 1 3 2 4 3 5 4 7 5 8 6 9 7 10 8 12 9 13 10 14 11 15 1217 13 18 14 19 15 20

When the bandwidth is 160 M, and another rate is used for the HE-SIGfield transmission (according to a case of the MCS and the DCM, or inother words, other than the foregoing cases), the coefficient factoris 1. In other words, in other cases, the value of the B18-B21 in theHE-SIG-A 1 is the same as the actual quantity of OFDM symbols in theHE-SIG-B indicated by the value of the B18-B2.

Example 2: A Bandwidth is 80 M (Including Two Puncturing Modes in the 80M)

Based on Formula 1, for example, the 80 M bandwidth is divided into amaximum of 37 resource units, and a quantity of information bitsincluded in an HE-SIG-B content channel is 511, where N=2, a=1, and Z=18in Formula 1. Therefore, according to the quantity of data subcarriersincluded in each OFDM symbol in the foregoing cases in which thedifferent MCSs are used and whether the DCM is used, the following maybe obtained.

For the 80 M bandwidth, when the MCS0 and the DCM are used for theHE-SIG-B field transmission, 39 OFDM symbols in the HE-SIG-B arerequired. For the bandwidth 80 M, when the MCS0 is used for the HE-SIG-Bfield transmission without DCM, or the MCS1 and the DCM are used, 20OFDM symbols in the HE-SIG-B are required. In other cases, the requiredquantity of symbols in the HE-SIG-B is less than 16, in other words, thequantity is less than a value indicated by the field that is in theHE-SIG-A 1 and that is used to indicate the quantity of symbols in theHE-SIG-B. Therefore, the required quantity is not limited.

Therefore, based on the foregoing calculation, when the bandwidth is 80M, and the MCS0 and the DCM are used for the HE-SIG-B fieldtransmission, the coefficient factor is 2.4375. To be specific, thequantity of symbols in the HE-SIG-B=ceil{(the value of theB18-B21+1)*2.3475}. Specifically, for a correspondence between the valueof the B18-B21 in the HE-SIG-A 1 and the quantity of OFDM symbols in theHE-SIG-B indicated by the value of the B18-B21, refer to the foregoingTable 2.

When the MCS0 (no DCM), or the MCS1 and DCM are used for the HE-SIG-Bfield transmission, the coefficient factor is 1.25. To be specific, thequantity of symbols in the HE-SIG-B=ceil{(the value of theB18-B21+1)*1.25}, and a specific correspondence is shown in theforegoing Table 3.

When another rate is used for the HE-SIG field transmission (dependingon the MCS and the DCM), the coefficient factor is 1. In other words,the value of the B18-B21 in the HE-SIG-A 1 is the same as the actualquantity of OFDM symbols in the HE-SIG-B indicated by the value of theB18-B2.

Example 3: A Bandwidth is 40 M

Based on Formula 1, for example, the maximum 40 M bandwidth is dividedinto a maximum of 18 resource units, and a quantity of information bitsincluded in an HE-SIG-B content channel is 257, where N=1, a=0, and Z=9in Formula 1. Therefore, when the MCS0 and the DCM are used for theHE-SIG-B field transmission, 20 symbols in the HE-SIG-B are required. Inother cases, the required quantity of symbols in the HE-SIG-B is lessthan 16, and the required quantity is not limited by the HE-SIG-B symbolquantity field in the HE-SIG-A 1.

Therefore, based on the foregoing calculation, when the MCS0 and the DCMare used for the HE-SIG-B field transmission, the coefficient factor is1.25. To be specific, the quantity of symbols in the HE-SIG-B=ceil{(thevalue of the B18-B21+1)*1.25}, and a specific correspondence is shown inTable 3.

When another rate is used for the HE-SIG field transmission (dependingon the MCS and the DCM), the coefficient factor is 1. In other words,the value of the B18-B21 in the HE-SIG-A 1 is the same as the actualquantity of OFDM symbols in the HE-SIG-B indicated by the value of theB18-B2.

Example 4: A Bandwidth is 20 M

When any rate is used for the HE-SIG field transmission (depending onthe MCS and the DCM), the coefficient factor is 1. In other words, whenthe bandwidth is 20 M. and the value of the B18-B21 in the HE-SIG-A 1 isthe same as the actual quantity of OFDM symbols in the HE-SIG-Bindicated by the value of the B18-B2.

Based on the foregoing four cases, in a specific implementation, the802.11ax protocol specifies that the quantity of symbols in theHE-SIG-B=ceil(the value of the B18-B21 in the HE-SIG-A+1)*coefficientfactor, and the coefficient factor depends on an MCS field, a DCM field,and a bandwidth field in the HE-SIG-A field. The coefficient factor isnot limited to the foregoing values such as 4.875, 2.4375, and 1.25,provided that a maximum value obtained by multiplying the coefficientfactor is greater than the required quantity of symbols in the HE-SIG-B.Certainly, if the maximum value is excessively large, there is excessiveredundant symbols in the HE-SIG-B, and overheads are increased.

In another manner: the 802.11ax protocol specifies that the quantity ofsymbols in the HE-SIG-B=ceil(the value of the B18-B21 in theHE-SIG-A+1)*coefficient factor, and the coefficient factor depends on anMCS field and a DCM field in the HE-SIG-A field. The coefficient factoris subject to the coefficient factor specified when a maximum bandwidthis 160 M, and the 20 M bandwidth is an exception. When the bandwidth is20 M, the coefficient factor is 1.

In another alternative implementation:

Based on the 802.11ax draft 2.0, a field M (namely, the B18-B21) that isin the HE-SIG-A 1 field and that is used to indicate the quantity ofOFDM symbols in the HE-SIG-B and a field (a B22) used to indicateHE-SIG-B compression are used to jointly indicate the quantity of OFDMsymbols in the HE-SIG-B.

Specifically, when the HE-SIG-B compression field B22=0, the quantity ofsymbols in the HE-SIG-B is equal to the value of the HE-SIG-B field (theB18-B21)+1. In this case, a minimum value is 1, and a maximum value is16.

When the HE-SIG-B compression field B22=1, and the value of the HE-SIG-Bfield (the B18-B21)<=7, a quantity of MU-MIMO stations participating ina full bandwidth is equal to the value of the field M (the B18-B21)+1.When the HE-SIG-B compression field (the B22)=1, and the value of thefield M (the B18-B21)>7, the quantity of OFDM symbols in the HE-SIG-B isequal to the value of the HE-SIG-B field B18-B21+1+8. In this case, aminimum value is 17 and a maximum value is 24. In conclusion, theHE-SIG-B symbol field B18-B21 and the HE-SIG-B compression field B22 inthe HE-SIG-A 1 field jointly indicate that a quantity of symbols in theHE-SIG-B ranges from 1 to 24.

In a specific example, the foregoing indicated value may be applicableonly to: another transmission rate for the HE-SIG-B other than thefollowing cases: the MCS0 and the DCM are used for the HE-SIG-B, oranother rate other than the MCS0 (no DCM), or the MCS1 and the DCM areused for the HE-SIG-B. Certainly, the value may also be applicable toall transmission rates.

In another example, for the foregoing three cases: the MCS0 and the DCMare used for the HE-SIG-B, or the MCS0 (no DCM) is used for theHE-SIG-B, or the MCS1 and the DCM are used for the HE-SIG-B, the threecases includes the following cases.

As mentioned above, based on the 802.11ax draft 2.0, the HE-SIG-B MCSfield in the HE-SIG-A 1 field (B1-B3) is used to indicate an MCS usedfor the HE-SIG-B. Values 0 to 5 of the B1-B3 respectively indicate MCSs0 to 5 used for the HE-SIG-B. In addition, values 6 and 7 of the B1-B3are reserved bits.

Specifically, when the value of the B1-B3 is 0, the value indicates thatthe MCS0 is used for the HE-SIG-B, and in this case, the quantity ofsymbols in the HE-SIG-B is a value jointly indicated by the HE-SIG-A 1field B18-B21 and the HE-SIG-B compression field (B22). In this case, aminimum value is 1, and a maximum value is 24.

When the value of B1-B3 is 6, the value indicates that the MCS0 is usedfor the HE-SIG-B symbol, and in this case, the quantity of symbols inthe HE-SIG-B is the value jointly indicated by the HE-SIG-A 1 field(B18-B21) and the HE-SIG-B compression field (B22)+24. In this case, aminimum value is 25, and a maximum value is 48.

When the value of DCM field (B4) in the HE-SIG-A 1 field is 1, itindicates that the DCM is used for the HE-SIG-B. In the following threecases, a value obtained after the value jointly indicated by theHE-SIG-A 1 field B18-B21 and the HE-SIG-B compression field B22 ismultiplied by the coefficient factor 2 is used to indicate the quantityof symbols in the HE-SIG-B. Otherwise, the jointly indicated value isthe indicated quantity of symbols in the HE-SIG-B, or is multiplied bythe coefficient factor 1. The following specific cases are included.

When the value of B1-B3 is 0 and B4=1, it indicates that the MCS0 andthe DCM are used for the HE-SIG-B symbol, and in this case, the quantityof symbols in the HE-SIG-B is (the value jointly indicated by theHE-SIG-A 1 field B18-B21 and the HE-SIG-B compression field B22)*2. Inthis case, a minimum value is 2, and a maximum value is 48.

When the value of B1-B3 is 6, and B4=1, it indicates that the MCS0 andthe DCM are used for the HE-SIG-B symbol, and in this case, the quantityof symbols in the HE-SIG-B is (the value jointly indicated by theHE-SIG-A 1 field B18-B21 and the HE-SIG-B compression field B22+24)*2.In this case, a minimum value is 50, and a maximum value is 96.

When the value of B1-B3 is 1, and B4=1, it indicates that the MCS1 andthe DCM are used for the HE-SIG-B symbol, and in this case, the quantityof symbols in the HE-SIG-B is (the value jointly indicated by theHE-SIG-A 1 field B18-B21 and the HE-SIG-B compression field B22)*2. Inthis case, a minimum value is 2, and a maximum value is 48.

In another alternative implementation:

Based on the 802.11ax draft 2.0, the HE-SIG-B MCS field in the HE-SIG-A1 field (B1-B3) is used to indicate an MCS used for the HE-SIG-B. Values0 to 5 of the B1-B3 respectively indicate MCSs 0 to 5 used for theHE-SIG-B. In addition, values 6 and 7 of the B1-B3 are reserved bits.

When the value of the B1-B3 is 0, the value indicates that the MCS0 isused for the HE-SIG-B symbol, and in this case, the quantity of symbolsin the HE-SIG-B is a value of the HE-SIG-A 1 field B18-B21+1. In thiscase, a minimum value is 1, and a maximum value is 16.

When the value of the B1-B3 is 6, the value indicates that the MCS0 isused for the HE-SIG-B symbol, and in this case, the quantity of symbolsin the HE-SIG-B is a value of the HE-SIG-A 1 field B18-B21+1+16. In thiscase, a minimum value is 17, and a maximum value is 32.

When the value of the B1-B3 is 7, the value indicates that the MCS0 isused for the HE-SIG-B symbol, and in this case, the quantity of symbolsin the HE-SIG-B is a value of the HE-SIG-A 1 field B18-B21+1+32+16. Inthis case, a minimum value is 33, and a maximum value is 48.

When the DCM field B4 in the HE-SIG-A 1 field is 1, it indicates thatthe DCM is used for the HE-SIG-B, and in the foregoing three cases, thequantity of symbols (independently) indicated by the B18-B21 in theHE-SIG-A 1 field is multiplied by the coefficient factor 2. Otherwise,the quantity remains unchanged or the quantity is multiplied by thecoefficient factor 1, and this specifically includes the followingcases.

When the value of the B1-B3 is 0, and B4=1, it indicates that the MCS0is used for the HE-SIG-B symbol, and in this case, the quantity ofsymbols in the HE-SIG-B is (the value of the B18-B21 in the HE-SIG-A 1field+1)*2. In this case, a minimum value is 2, and a maximum value is32.

When the value of the B1-B3 is 6, and B4=1, it indicates that the MCS0is used for the HE-SIG-B symbol, and in this case, the quantity ofsymbols in the HE-SIG-B is (the value of the B18-B21 in the HE-SIG-A 1field+1+16)*2. In this case, a minimum value is 34, and a maximum valueis 64.

When the value of the B1-B3 is 7, and B4=1, it indicates that the MCS0is used for the HE-SIG-B symbol, and in this case, the quantity ofsymbols in the HE-SIG-B is (the value of the B18-B21 in the HE-SIG-A 1field+1+32)*2. In this case, a minimum value is 66, and a maximum valueis 96.

Another implementation of the present invention provides an apparatusthat can implement one of the foregoing methods. Optionally, a sendingapparatus 500 is an AP or a chip on an AP, and a receiving apparatus 600is a terminal or a chip on a terminal.

The embodiments of the present invention can be applied to variouscommunications devices.

Referring to FIG. 5, a transmitter of the sending apparatus 500 mayinclude a transmitting circuit, a power controller, an encoder, and anantenna. In addition, the device 500 may further include a receiver. Thereceiver may include a receiving circuit, a power controller, a decoder,and an antenna.

A processor may also be referred to as a CPU. A memory may include aread-only memory and a random access memory, and provide an instructionand data to the processor. A part of the memory may further include anon-volatile random access memory (NVRAM). In a specific application,the device 500 may be built in or the device 500 may be a wirelesscommunications device such as a network device, and may further includea carrier including a transmitting circuit and a receiving circuit, toallow data transmission and reception between the device 500 and aremote location. The transmitting circuit and the receiving circuit maybe coupled into an antenna. Components of the device 500 are coupledtogether by using a bus, and the bus further includes a power supplybus, a control bus, and a status signal bus in addition to a data bus.Certainly, the bus may be another replaced connection circuit. However,for clarity of description, various buses are marked as the bus in thefigure. In different specific products, the decoder may be integratedwith a processing unit.

The processor can implement or execute the steps and the logical blockdiagrams that are disclosed in the method embodiments of the presentinvention. A general-purpose processor may be a microprocessor, or theprocessor may be any conventional processor, decoder, or the like. Thesteps in the method disclosed with reference to the embodiments of thepresent invention may be directly performed by a hardware processor, ormay be performed by using a combination of hardware and a softwaremodule in a decoding processor. The software module may be located in amature storage medium in the art, such as a random access memory, aflash memory, a read-only memory, a programmable read-only memory, anelectrically erasable programmable memory, or a register.

It should be understood that in the embodiments of the presentinvention, the processor may be a central processing unit (“CPU” forshort), or the processor may be another general-purpose processor, adigital signal processor (DSP), an application-specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or anotherprogrammable logic device, a discrete gate or a transistor logic device,a discrete hardware component, or the like. The general-purposeprocessor may be a microprocessor, or the processor may be anyconventional processor, or the like.

The memory may include a read-only memory and a random access memory,and provide an instruction and data to the processor. A part of thememory may further include a non-volatile random access memory. Forexample, the memory may further store information about a device type.

A bus system may further include a power bus, a control bus, a statussignal bus, and the like, in addition to a data bus. However, forclarity of description, various buses are marked as the bus system inthe figure.

In an implementation process, steps in the foregoing methods can beimplemented by using an integrated logic circuit of hardware in theprocessor, or by using instructions in a software form. The steps in themethod disclosed with reference to the embodiments of the presentinvention may be directly performed by a hardware processor, or may beperformed by using a combination of hardware and a software module inthe processor. The software module may be located in a mature storagemedium in the art, such as a random access memory, a flash memory, aread-only memory, a programmable read-only memory, an electricallyerasable programmable memory, or a register. The storage medium islocated in the memory, and the processor reads information in the memoryand implements the steps in the foregoing methods in combination withhardware of the processor. To avoid repetition, details are notdescribed herein again.

The sending apparatus 500 according to this embodiment of the presentinvention may be corresponding to a transmit end in the method in theembodiments of the present invention (for example, the AP). In addition,all units, namely, modules, of the sending apparatus 500 and theforegoing and other operations and/or functions are separately intendedto implement corresponding procedures of the implementations. Forbrevity, details are not described herein.

FIG. 6 is a schematic block diagram of a receiving apparatus 600according to an embodiment of the present invention. The receivingapparatus 600 is applied to a wireless local area network, and theapparatus 600 includes:

a bus 610, where the bus 610 may certainly be another replacedconnection circuit:

a processor 620 connected to the bus;

a memory 630 connected to the bus; and

a receiver 640 connected to the bus.

The processor invokes a program stored in the memory by using the bus,to use the program for the method mentioned in the foregoingimplementations, and details are not described herein again.

Optionally, a transmit end is a network device, and the device 600 is aterminal device.

The embodiments of the present invention can be applied to variouscommunications devices.

A receiver of the device 600 may include a receiving circuit, a powercontroller, a decoder, and an antenna, and the device 600 may furtherinclude a transmitter, and the transmitter may include a transmittingcircuit, a power controller, an encoder, and an antenna.

The processor may also be referred to as a CPU. The memory may include aread-only memory and a random access memory, and provide an instructionand data to the processor. A part of the memory may further include anon-volatile random access memory (NVRAM). In a specific application,the device 600 may be built in or the device 600 may be a wirelesscommunications device such as a terminal device, and may further includea carrier including a transmitting circuit and a receiving circuit, toallow data transmission and reception between the device 600 and aremote location. The transmitting circuit and the receiving circuit maybe coupled into an antenna. Components of the device 600 are coupledtogether by using a bus, and the bus further includes a power supplybus, a control bus, and a status signal bus in addition to a data bus.However, for clarity of description, various buses are marked as the busin the figure. In different specific products, the decoder may beintegrated with a processing unit.

The processor can implement or execute the steps and the logical blockdiagrams that are disclosed in the method embodiments of the presentinvention. A general-purpose processor may be a microprocessor, or theprocessor may be any conventional processor, decoder, or the like. Thesteps in the method disclosed with reference to the embodiments of thepresent invention may be directly performed by a hardware processor, ormay be performed by using a combination of hardware and a softwaremodule in a decoding processor. The software module may be located in amature storage medium in the art, such as a random access memory, aflash memory, a read-only memory, a programmable read-only memory, anelectrically erasable programmable memory, or a register.

It should be understood that in the embodiments of the presentinvention, the processor may be a central processing unit (“CPU” forshort), or the processor may be another general-purpose processor, adigital signal processor (DSP), an application-specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or anotherprogrammable logic device, a discrete gate or a transistor logic device,a discrete hardware component, or the like. The general-purposeprocessor may be a microprocessor, or the processor may be anyconventional processor, or the like.

The memory may include a read-only memory and a random access memory,and provide an instruction and data to the processor. A part of thememory may further include a non-volatile random access memory. Forexample, the memory may further store information about a device type.

A bus system may further include a power bus, a control bus, a statussignal bus, and the like, in addition to a data bus. However, forclarity of description, various buses are marked as the bus system inthe figure.

In an implementation process, steps in the foregoing methods can beimplemented by using an integrated logic circuit of hardware in theprocessor, or by using instructions in a software form. The steps in themethod disclosed with reference to the embodiments of the presentinvention may be directly performed by a hardware processor, or may beperformed by using a combination of hardware and a software module inthe processor. The software module may be located in a mature storagemedium in the art, such as a random access memory, a flash memory, aread-only memory, a programmable read-only memory, an electricallyerasable programmable memory, or a register. The storage medium islocated in the memory, and the processor reads information in the memoryand implements the steps in the foregoing methods in combination withhardware of the processor. To avoid repetition, details are notdescribed herein again.

The apparatus 600 according to this embodiment of the present inventionmay be corresponding to a receive end in the method in the embodimentsof the present invention (for example, the terminal device). Inaddition, all units, namely, modules, of the sending apparatus 500 andthe foregoing and other operations and/or functions are separatelyintended to implement corresponding procedures of the foregoingimplementations. For brevity, details are not described herein.

It should be understood that sequence numbers of the foregoing processesdo not mean execution sequences in the embodiments of the presentinvention. The execution sequences of the processes should be determinedbased on functions and internal logic of the processes, and should notbe construed as any limitation on the implementation processes of theembodiments of the present invention.

A person of ordinary skill in the art may be aware that, the units andalgorithm steps in the examples described with reference to theembodiments disclosed in this specification can be implemented byelectronic hardware or a combination of computer software and electronichardware. Whether the functions are performed by hardware or softwaredepends on particular applications and design constraints of thetechnical solutions. A person skilled in the art may use differentmethods to implement the described functions for each particularapplication, but it should not be considered that the implementationgoes beyond the scope of the present invention.

It may be clearly understood by a person skilled in the art that for thepurpose of convenient and brief description, for a detailed workingprocess of the described system, apparatus, and unit, refer to acorresponding process in the foregoing method embodiments. Details arenot described herein again.

In the several embodiments provided in this application, it should beunderstood that the disclosed system, apparatus, and method may beimplemented in other manners. For example, the described apparatusembodiment is merely an example. For example, the unit division ismerely logical function division and may be other division in actualimplementation. For example, a plurality of units or components may becombined or integrated into another system, or some features may beignored or not performed. In addition, the displayed or discussed mutualcouplings or direct couplings or communication connections may beimplemented by using some interfaces. The indirect couplings orcommunication connections between the apparatuses or units may beimplemented in electronic, mechanical, or other forms.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,may be located in one position, or may be distributed on a plurality ofnetwork units. Some or all of the units may be selected according toactual requirements to achieve the objectives of the solutions of theembodiments.

In addition, function units in the embodiments of the present inventionmay be integrated into one processing unit, or each of the units mayexist alone physically, or two or more units are integrated into oneunit.

When functions are implemented in the form of a software function unitand sold or used as an independent product, the functions may be storedin a computer-readable storage medium. Based on such an understanding,the technical solutions of the present invention essentially, or thepart contributing to the prior art, or some of the technical solutionsmay be implemented in a form of a software product. The computersoftware product is stored in a storage medium, and includes severalinstructions for instructing a computer device (which may be a personalcomputer, a server, a transmit end, or the like) to perform all or someof the steps of the methods in the embodiments of the present invention.The foregoing storage medium includes various media that can storeprogram code, such as a USB flash drive, a removable hard disk, aread-only memory (ROM), a random access memory (RAM), a magnetic disk,or an optical disc.

The foregoing descriptions are merely specific embodiments of thepresent invention, but are not intended to limit the protection scope ofthe present invention. Any variation or replacement readily figured outby a person skilled in the art within the technical scope disclosed inthe present invention shall fall within the protection scope of thepresent invention. Therefore, the protection scope of the presentinvention should be subject to the protection scope of the claims.

What is claimed is:
 1. A radio physical layer protocol data unit (PPDU)sending method, comprising: obtaining, a radio physical layer protocoldata unit (PPDU), wherein the PPDU includes a high efficiency-signalfield A (HE-SIG-A) and a high efficiency-signal field B (HE-SIG-B), theHE-SIG-A includes a field indicating a quantity of orthogonal frequencydivision multiplexing (OFDM) symbols in the HE-SIG-B, and wherein avalue of the field indicates one of the following: that the quantity ofOFDM symbols included in the HE-SIG-B is greater than or equal to 16, orthe quantity of OFDM symbols included in the HE-SIG-B; and sending thePPDU.
 2. The method according to claim 1, wherein the field is B18-B21in the HE-SIG-A; and when a value of the B18-B21 is any value of 0 to14, the quantity of OFDM symbols included in the HE-SIG-B is equal to avalue of the B18-B21+1; and when a value of the B18-B21 is 15, thequantity of OFDM symbols included in the HE-SIG-B is greater than orequal to
 16. 3. The method according to claim 2, wherein the HE-SIG-Afurther includes a B22, when a value of the B22 is 0, the value of theB18-B21 indicates the quantity of OFDM symbols in the HE-SIG-B, and whena value of the B22 is 1, the value of the B18-B21 indicates a quantityof stations participating in multi-user multiple-input multiple-outputtransmission.
 4. A radio physical layer protocol data unit (PPDU)receiving method, comprising: receiving a radio physical layer protocoldata unit (PPDU), wherein the PPDU includes a high efficiency-signalfield A (HE-SIG-A) and a high efficiency-signal field B (HE-SIG-B), theHE-SIG-A includes a field indicating a quantity of orthogonal frequencydivision multiplexing (OFDM) symbols in the HE-SIG-B, and wherein avalue of the field indicates one of the following: that the quantity ofOFDM symbols included in the HE-SIG-B is greater than or equal to 16, orthe quantity of OFDM symbols included in the HE-SIG-B; and determining,based on the received HE-SIG-A, the quantity of OFDM symbols in theHE-SIG-B or an end position of the HE-SIG-B.
 5. The method according toclaim 4, wherein the field is B18-B21 in the HE-SIG-A; and thedetermining, based on the received HE-SIG-A, the quantity of OFDMsymbols in the HE-SIG-B or the end position of the HE-SIG-B comprises:if a value of the B18-B21 is any value of 0 to 14, determining that thequantity of OFDM symbols in the HE-SIG-B is M, wherein M is the value ofthe B18-B21+1: or if a value of the B18-B21 is 15, obtaining stationquantity information based on a common field in the HE-SIG-B, anddetermining the quantity of OFDM symbols included in the HE-SIG-B basedon the station quantity information.
 6. The method according to claim 5,wherein the HE-SIG-A includes a B22, when a value of the B22 is 0, thevalue of the B18-B21 indicates the quantity of OFDM symbols in theHE-SIG-B, and when a value of the B22 is 1, the value of the B18-B21indicates a quantity of stations participating in multi-usermultiple-input multiple-output transmission.
 7. A radio physical layerprotocol data unit (PPDU) sending apparatus, comprising: anon-transitory memory storage comprising instructions; and one or morehardware processors in communication with the non-transitory memorystorage, wherein the one or more hardware processors execute theinstructions to: obtain a radio physical layer protocol data unit(PPDU), wherein the PPDU includes a high efficiency-signal field A(HE-SIG-A) and a high efficiency-signal field B (HE-SIG-B), and theHE-SIG-A includes a field indicating a quantity of orthogonal frequencydivision multiplexing (OFDM) symbols in the HE-SIG-B, and wherein avalue of the field indicates one of the following: that the quantity ofOFDM symbols included in the HE-SIG-B is greater than or equal to 16, orthe quantity of OFDM symbols included in the HE-SIG-B; and atransmitter, configured to send the PPDU.
 8. The apparatus according toclaim 7, wherein the field is B18-B21 in the HE-SIG-A; and when a valueof the B18-B21 is any value of 0 to 14, the quantity of OFDM symbolsincluded in the HE-SIG-B is equal to a value of the B18-B21+1; and whena value of the B18-B21 is 15, the quantity of OFDM symbols included inthe HE-SIG-B is greater than or equal to
 16. 9. The apparatus accordingto claim 8, wherein the HE-SIG-A further includes a B22, when a value ofthe B22 is 0, the value of the B18-B21 indicates the quantity of OFDMsymbols in the HE-SIG-B, and when a value of the B22 is 1, the value ofthe B18-B21 indicates a quantity of stations participating in multi-usermultiple-input multiple-output transmission.
 10. A radio physical layerprotocol data unit (PPDU) receiving apparatus, comprising: a receiver,configured to receive a radio physical layer protocol data unit (PPDU),wherein the PPDU includes a high efficiency-signal field A (HE-SIG-A)and a high efficiency-signal field B (HE-SIG-B), the HE-SIG-A includes afield indicating a quantity of orthogonal frequency divisionmultiplexing (OFDM) symbols in the HE-SIG-B, and wherein a value of thefield indicates one of the following: that the quantity of OFDM symbolsincluded in the HE-SIG-B is greater than or equal to 16, or the quantityof OFDM symbols included in the HE-SIG-B; a non-transitory memorystorage comprising instructions; and one or more hardware processors incommunication with the non-transitory memory storage, wherein the one ormore hardware processors execute the instructions to: determine, basedon the received HE-SIG-A, the quantity of OFDM symbols in the HE-SIG-Bor an end position of the HE-SIG-B.
 11. The apparatus according to claim10, wherein the field is B18-B21 in the HE-SIG-A; and the one or morehardware processors execute the instructions to: if a value of theB18-B21 is any value of 0 to 14, determine that the quantity of OFDMsymbols in the HE-SIG-B is M, wherein M is the value of the B18-B21+1;or if a value of the B18-B21 is 15, obtain station quantity informationbased on a common field in the HE-SIG-B, and determine the quantity ofOFDM symbols included in the HE-SIG-B based on the station quantityinformation.
 12. The apparatus according to claim 11, wherein theHE-SIG-A includes a B22, when a value of the B22 is 0, the value of theB18-B21 indicates the quantity of OFDM symbols in the HE-SIG-B, and whena value of the B22 is 1, the value of the B18-B21 indicates a quantityof stations participating in multi-user multiple-input multiple-outputtransmission.